To further introduce the concept of polarization in heterophilic adhesion, we consider the multipole expansion of \(\rho (\mathbf {r})\)  [1]}, [2]}, [3]}:
\(\rho _m(\mathbf {r}) = \rho _m^{\rm M} + \rho _m^{\rm D}(\mathbf {e}_m(\mathbf {r})\cdot \mathbf {p}_m)+ \dots .\) 
